Topiramate interactions

Topiramate interacts with other antiepileptic agents, including carbamazepine, phenytoin, and vaiproate, resulting in more rapid metabolism and elimination and reduced plasma concentration of topiramate. Carbamazepine can reduce topiramate serum levels by up to 25%. Phenytoin can lower topiramate serum levels by up to 25%, while topiramate has been shown to increase phenytoin serum levels by about 50%. 

Topiramate Topamax Suspension 300 mg/5 mL Tablet 25, 100, 200 mg Doses should be slowly adjusted up and down according to response and adverse effects (e.g., 150-300 mg twice daily and increase by 300-600 mg/day at weekly intervals) 50-200 mg/day in divided doses drug-drug interactions than carbamazepine, but causes more gastrointestinal side effects and hyponatremia Evidence is limited regarding efficacy Not recommended for the... 

II.e. 5.2. Interactions between first and second generation AEDs. Felbamate raises plasma concentrations of phenytoin, valproic acid and carbamazepine. Clearance of tiagabine, topiramate and zon-isamide is increased in the presence of an enzyme inducer. Vigabatrin reduces phenytoin concentrations after 4-5 weeks of comedication (via an unknown mechanism). For tiagabine, the elimination half-life may be reduced by 2-3 hours in the presence of an enzyme-induction AED. Lamotrigine elimination is slower if given with valproic acid. Topiramate reduces elimination of phenytoin. 

Drug interactions involving AEDs are shown in Table 52-5. Phenobarbital, phoiytom, primidone and carbamazepine are potent inducers of cytochrome P450 (CYP450), epoxide hydrolase, and uridine diphosphate gjucuronosyltransferase enzyme systems. Valproic acid inhibits many hepatic enzjrme systems and displaces some drugs from plasma albumin. Felbamate and topiramate can act as inducers with some isoforms and inhibitors with others. 

TOPIRAMATE ANTIDIABETIC DRUGS-METFORMIN T metformin levels Unknown mechanism Watch for and warn patients about hypoglycaemia - For signs and symptoms of hypoglycaemia, see Clinical Features of Some Adverse Drug Interactions, Hypoglycaemia... 

Topiramate may interact A/ith carbonic anhydrase inhibitors to increase the risk of kidney stones... 

Topiramate Phenytoin 2006 Elsevier B.V. All rights reserved. Interaction inconsistent, usually of little clinical significance Inhibition of phenytoin metabolism Continued... 

Topiramate slightly impairs digoxin clearance (53), but the interaction is probably not clinically significant. 

Three children taking valproate developed hyperammonemia after topiramate was added (56). Ammonia was normalized after topiramate was reduced or withdrawn. Thus, topiramate could potentially enhance the risk of hyperammonemia in patients taking valproate. The authors did not discuss the mechanism of this purported interaction. 

Clinically important, potentially hazardous interactions with carbamazepine, lamotrigine, phenobarbital, primidone, topiramate, valproic acid, vigabatrin... 

Gidal BE. Topiramate Drug interactions. In Levy RH, Mattson RH, Meldrum BS, et al, eds. Antiepileptic Drugs, 5th ed. Philadelphia, Lippincott Williams Wilkins, 2002 735-739. 

I Drug-Drug Interactions. Carbamazepine induces the hepatic cytochrome P450 isoenzymes (1A2, 3A4, 2C9/10, and 2D6), which increases the metabolism of many medications, such as anticonvulsants (i.e., lamotrigine, topiramate, and valproate), antidepressants (i.e., tricyclics and bupropion), antipsychotics (i.e., clozapine, haloperi-dol, fluphenazine, olanzapine, and thiothixene), benzodiazepines, oral contraceptives, and protease inhibitors. " Women who receive carbamazepine require higher dosages of oral contraceptives or alternative contraceptive methods." ... 

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